Method and apparatus for remotely controlling a welding system

ABSTRACT

The present invention is directed to a remote control that uses a welding circuit to transfer control information to a welding power source. The information to be communicated to the power source includes welding power source output command information (amperage/voltage control), welding circuit on/off information (power source output contactor control), and power source mode control (constant voltage/constant current). The control information may be transmitted in a serial communication and/or encoded using frequency and or voltage coding. The control information may be transmitted during dedicated transmission intervals or as an offset to an open circuit voltage between the power source and wire feeder.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a divisional and claims priority of U.S.patent application Ser. No. 10/904,172 filed Oct. 27, 2004, thedisclosure of which is incorporated herein.

BACKGROUND OF THE INVENTION

The present invention relates generally to welding machines and, moreparticularly, to a method and apparatus for remotely controllingoperation of a power source of a welding-type system through thetransmission of control signals across a weld cable.

MIG welding, formerly known as Gas Metal Arc Welding (GMAW), combinesthe techniques and advantages of TIG welding's inert gas shielding witha continuous, consumable wire electrode. An electrical arc is createdbetween the continuous, consumable wire electrode and a workpiece. Assuch, the consumable wire functions as the electrode in the weld circuitas well as the source of filler metal. MIG welding is a relativelysimple process that allows an operator to concentrate on arc control.MIG welding may be used to weld most commercial metals and alloysincluding steel, aluminum, and stainless steel. Moreover, the travelspeed and the deposition rates in MIG welding may be much higher thanthose typically associated with either Gas Tungsten Arc Welding (TIG) orShielded Metal Arc Welding (stick) thereby making MIG welding a moreefficient welding process. Additionally, by continuously feeding theconsumable wire to the weld, electrode changing is minimized and assuch, weld effects caused by interruptions in the welding process arereduced. The MIG welding process also produces very little or no slag,the arc and weld pool are clearly visible during welding, and post-weldclean-up is typically minimized. Another advantage of MIG welding isthat it can be done in most positions which can be an asset formanufacturing and repair work where vertical or overhead welding may berequired.

A wire feeder is operationally connected to the power source and isdesigned to deliver consumable wire to a weld. To further enhance theoperability of the wire feeder of a MIG welding system, known weldingsystems have connected the power source and the wire feeder to oneanother across a dedicated control cable that is in addition to adedicated weld cable such that control signals defining the operationalparameters of the power source are transmitted or fed back from the wirefeeder to the power source, generally referred to as remote control.

One type of remote control device is used to regulate the operationalwelding parameters, and switch the welding power source output ON andOFF as well as change the power source mode via a pendant that connectsto the power source by a multi-conductor cable. The solution isschematically illustrated in FIG. 1A. A wire feeder 2A is connected to apower source 4A by a control cable 6A that includes a 14-pin connector.The cable 6A used to transmit operational information to, and in somecases, from the power source may incorporate 2 to 14 conductorsdepending on how many functions are to be controlled. Separatelyconnected between the power source 4A and wire feeder 2A is a highvoltage weld cable 8A that delivers welding power to the wire feeder andcreates a voltage potential between an electrode and a workpiece.

A significant drawback to this control cable-based scheme is that thecontrol cable is typically fragile relative to the welding cablesdesigned to carry high currents at high voltages. Welding machines arecommonly used at construction sites or shipyards where it is notuncommon for the welding machines to be periodically relocated orsurrounded by other mobile heavy equipment operating in the same area.As such, the remote control cable can become damaged by being crushed orsnagged from contact with surrounding machines and/or traffic. This cancause damage to the wire feeder and/or the welding power source ifinternal power conductors become shorted to signal leads that areconnected to sensitive signal level circuitry.

Referring now to FIG. 1B, another remote controlled system includes aradio transmitter type remote control. This approach has severaldisadvantages. First, electric arc welding can create radio frequencyinterference that negatively affects the communication between atransceiver 9A of the wire feeder 2B and the transceiver 9B of the powersource 4B. Second, if the system is used inside metal structures such astanks, ships, or large aircraft, the radio link can be lost due to theshielding effect of the metallic surroundings. Third, if multiplewelding stations use a radio link for remote control, each control loopwould require a separate security code to prevent cross-talk ormis-transmission of control signals to the wrong welding machine.

Another remote control solution is described in U.S. Ser. No.10/604,482, which is assigned to the Assignee of the presentapplication. Notwithstanding the numerous advancements achieved with theinvention of the aforementioned pending application, such a systemrelies upon pulse width modulation to remotely transmit operational datafrom a wire feeder to a power source across a weld cable. By using pulsewidth modulated signals to remotely control operation of a power source,the amount of data as well as variability in the types of data thatcould be transmitted between the wire feeder and a power source islimited when compared to that which may be achieved with serialized orencoded communications. Further, with the system described in theaforementioned pending application, the wire feeder is constructedwithout a contactor and thus requires an internal DC power supply topower the electronics of the wire feeder. That is, the invention of theabove-referenced application teaches the avoidance of an open circuitvoltage (OCV) between the wire feeder and power source. As a result,absent a DC power supply, the wire feeder cannot be minimally powered soas to communicate with the power source to initiate the welding process.

It is therefore desirable to design a remote controlled welding machinethat receives command signals from a wire feeder across a weld cable tocontrol or otherwise regulate operation of a power source. It would alsobe desirable to design a remote controlled welding system having with abattery-less wire feeder whereupon electronics of the wire feeder arepowered in a conventional manner, but the OCV between the wire feederand power source is used as the backbone of a communications linkbetween the wire feeder and power source for the transmission of controlcommands.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides a system and method of remotelycontrolling operation of a welding machine via control commandstransmitted across a weld cable connecting the welding machine to aperipheral, such as a wire feeder, that overcomes the aforementioneddrawbacks.

A remote control uses a weld cable as a communication link to transfercontrol information to a welding power source. The information to becommunicated to the power source includes welding power source outputcommand information (amperage/voltage control), welding circuit on/offinformation (power source output contactor control), power source modecontrol (constant voltage/constant current), and the like. The controlinformation may be transmitted in a serial communication and/or encodedusing frequency and or voltage decoding. The control information may betransmitted during dedicated transmission intervals or as an offset toan OCV between the power source and wire feeder.

Therefore, in accordance with one aspect, the present invention includesa welding system having a battery-less wire feeder designed to feedconsumable material to a weld and a power source designed to provide awelding power and having a power output connected to the battery-lesswire feeder via a weld cable. The welding system includes a controllerto periodically disable the power output and receive power sourcecontrol commands from the battery-less wire feeder across the weld cablewhen the power output is disabled.

In accordance with another aspect, a MIG welder is disclosed andincludes a wire feeder designed to deliver consumable welding wire to aweld. A power source is connected to the wire feeder via a weld cable.The weld cable is designed to carry an OCV thereacross during standbyoperation of the wire feeder. The MIG welder includes a communicationslink between the wire feeder and the power source extending across theweld cable. The communications link is designed to translate controlcommands between the power source and wire feeder manifested in avoltage offset from the OCV.

According to yet another aspect, the present invention includes a methodof remotely controlling a welding process. The method includes the stepsof periodically disabling an output of a power source designed toprovide welding power to a weld and receiving control commands from awire feeder remote from the power source when the output of the powersource is disabled. The method further includes the step of, followingreception of the control commands, re-enabling the output of the powersource to provide power to the weld at a level consistent with thatembodied in the control commands.

Various other features, objects and advantages of the present inventionwill be made apparent from the following detailed description and thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate one preferred embodiment presently contemplatedfor carrying out the invention.

In the drawings:

FIGS. 1A-1B are schematic block diagrams illustrating examples of knownremotely controlled welding and wire feeder systems.

FIG. 2 is a pictorial view of a welding system in accordance with oneaspect of the present invention.

FIG. 3 is a schematic of the welding system illustrated in FIG. 2.

FIG. 4 is a flow chart setting forth the steps of remotely controlling apower source in accordance with one aspect of the present invention.

FIG. 5 is an exemplary circuit schematic for providing an OCV offsetaccording to another aspect of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will be described with respect to regulation of apower source and a wire feeder of a MIG welding system based on feedbackprovided from a transceiver remote from the power source to a receiverincorporated within the power source. However, the present invention isequivalently applicable with power sources of TIG, stick, flux cored,and the like welding systems. Moreover, the present invention is alsoapplicable with non-welding, high power systems such as plasma cuttersand induction heaters.

Referring to FIGS. 2 and 3, a MIG welding system 10 includes a weldingpower source 12 designed to supply power to a wire feeder 14 through aweld cable 16. The power source is designed to run in one of a number ofmodes including constant voltage (CV) and constant current (CC). Alsoconnected to the power source is a secondary work weld cable 18 thatconnects the power source to a clamp 20 designed to receive cable 18 toworkpiece 22. Also connected to wire feeder 14 is a welding gun or torch24 configured to supply consumable welding wire to a weld. Weldingsystem 10 may further include a gas cylinder 26 connected to wire feeder14 such that shielding gas can be provided through gas hose 28 for theMIG welding process.

Power source 12 is designed to condition raw power supplied from autility line or engine driven power supply and output power usable bythe welding process. As such, power source 12 includes one or moretransformer assemblies or power conditioner 29 to condition the rawpower into a usable form for welding. The output of the power source isgenerally controlled by a controller 38 and associated operationalcircuitry that regulates the secondary or output side of the powerconditioning components 29. As such, the power source may provide awelding output when the secondary power circuit 39 and the contactor 41or other power switching device is closed to a conductive state. As willbe described in greater detail below, switch device 39 may be regulatedsuch that a secondary or welding power output is periodically notprovided to wire feeder 14 across weld cable 16 during non-weldingintervals. In this regard, the typically otherwise present OCV betweenthe power source and wire feeder is temporarily lost. During thesemoments of disablement of the power source output, transceiver 36 willawait control commands across weld cable 16 which then operates as thebackbone of a communication link between the wire feeder and the powersource.

Torch 24 is equipped with a pushbutton trigger 30 that when depressedcauses contactor 41 of the wire feeder to close and make a weldingvoltage available to the torch. As shown in FIGS. 2 and 3, a separatecontrol cord connecting the wire feeder and power source to one anotheris avoided.

The incorporation of a transceiver within wire feeder 14 thatcommunicates with a transceiver in power source 12 directly through weldcable 16 eliminates the need for a separate control/power cable. Thecontrol cable adds to the complexity, weight, and overall cost of thewelding system. Additionally, as previously noted, the control cord istypically less durable than the welding cables and, as such, is prone tonicks and snags typically associated with industrial locations.

This invention includes a pair of transceivers 36, 32: one in the powersource 12 and one in the wire feeder 14. In this regard, bi-directionalcommunication is supported between the wire feeder and the power source.It is contemplated, however, that the wire feeder may be equipped with atransmitter and the power source with a receiver to supportuni-directional communication between the two components. Thetransceiver in the wire feeder is designed to transmit serialized andmodulated packets of feedback or commands to a transceiver 36 in thepower source 12 across the weld cable 16.

The signal includes information regarding desired operational parametersof the wire feeder 14 and instructs the transceiver 36 of the powersource 12 to set the magnitude of the output of the welding power source(volts or amperes), the mode of the welding power source (CC or CV), andwire feed speed among other parameters. The transceiver 32 is alsoconfigured to transmit commands regarding JOG and PURGE functions. Thatis, when the JOG button is pushed on the wire feeder 14, the transmitautomatically repeats the minimum reference command each time the opencircuit voltage of the welding power source falls to zero. In accordancewith known wire feeder construction, the operator may select operationalparameters on a user panel of the wire feeder. In a further embodiment,the user panel may be integrated with the electrode holder or torch 24to allow user control of the welding process without leaving the weld.

Referring again to FIG. 3, the welding system 10 is designed to provideserialized and/or encoded communication between the wire feeder 14 andpower source 12. In this regard, controller 34 of wire feeder 14 alsoincludes an encoder 40, serializing circuitry 42, and modulator 43.Serializing circuitry 42 is designed to serialize communications betweenthe wire feeder and the power source based on user input to a user panel44 and for feedback provided from the weld. Encoder 40 is designed toencode the serialized transmission for improved and more efficienttransmission to the power source 12. Modulator 43 is designed tomodulate the serialized data before transmission. A number oftransmission techniques is envisioned including, but not limited tospread spectrum and psuedo-random sequenced using amplitude and/orphase-shifting. Spread spectrum technology is a method of communicationthat is typically implemented to secure communications and/or toovercome narrow-band constraints of a transmission line, i.e. aweld-cable. It is also contemplated that voltage and frequency levelencoding may be used.

As described above, user panel 44 is designed to receive discrete inputsfrom an operator that collectively define operation of a weldingprocess. As wire feeder 14 supports digitized control of the weldingprocess, the operator is able to input, with a certain degree ofspecificity, exact operating parameters via user panel 44. However, aswelding system 10 is a remotely controlled system, controller 34 of wirefeeder 14 receives the user inputs whereupon those inputs are fed toserializing circuit 42 to arrange the user input data into a serializedcommunication that supports streamlined transmission of the controlcommands across weld cable 16.

Power source 12 also includes a decoder 46 and demodulator 47 that arematched with the encoder 40 of the wire feeder so as to demodulate anddecipher the encoded signal received from transceiver 32 across weldcable 16. Based on the deciphered commands, controller 38 will regulateoperation of power source 12 in accordance with the user inputs to thewire feeder 14. In a further embodiment, each transmission includes achecksum that allows decoder 46 to verify the accuracy of thetransmitted data based on the particular encoding used.

Referring now to FIG. 4, a flow chart is shown setting forth steps ofremotely controlling a welding-type power source according to oneembodiment of the present invention. Preferably, the power sourcecontroller 38 carries out the steps of process 48 through the executionof one or more programs stored on a readable storage medium (not shown)in the power source. Process 48 begins at 50 with powering up at 52 ofthe power source to provide an OCV between the power source and the wirefeeder across the weld cable. This OCV is provided in a conventionalmanner. Specifically, the power conditioning components, i.e.transformer, of the power source receives a raw power input from eithera utility source or an engine-driven generator and conditions that powerinput into a form usable by a welding-type process. The OCV will bemaintained between the wire feeder and the power source across the weldcable and used to power the electronics of the wire feeder when the wirefeeder is in a standby mode. In a conventional manner, when thecontactor or other switch mechanism in the wire feeder is closed, thevoltage across the weld cable will be available at the welding torch orgun for creation of an arc between an electrode, i.e. consumable wire,and the workpiece. When this welding circuit is formed, the wire feederas well as the power source preferably operate consistent with theparameters identified by the operator and transmitted from the wirefeeder remotely to the power source. In this regard, process 48 ispreferably executed prior to the commencement of a welding-type processand also re-executed during non-welding intervals.

That is, when the OCV is available across the weld cable 52, thecontroller 38 will periodically disable the output of the power sourceat 54, 58. It should be noted that, in a preferred embodiment, the poweroutput is only disabled when a welding 54, 56 process is not activelybeing carried out 56. In this regard, the controller will determine thatthe contactor in the wire feeder has closed the welding circuit when theOCV is lost. While the power source output is disabled, the controllerwill query the receiver for control commands transmitted across the weldcable at 56. That is, if the operator indirectly opens the contactor inthe wire feeder to open the welding circuit, and the OCV between thewire feeder and power source is re-established, the controller of thepower source will briefly disable the power source output 58 and awaitcontrol commands 60 across the weld cable during this period ofdisablement. It is noted that the OCV will be briefly lost between thewire feeder and power source when the power source output is disabled.As such, any signal detected across the weld cable when the power sourceoutput is disabled will include control data from the wire feeder to theremote power source, and vice versa.

If control commands are received 60, 62 across the weld cable 56, 58,the controller processes the control data and adjusts 64 operation ofthe power source accordingly. On the other hand, if control data is notreceived 60, 66 during the brief disablement of the power source output,the controller will cause re-enablement 68 of the power source output,which will cause re-establishment of the OVC 52 between the wire feederand power source. The re-establishment of the OCV at 52 will bemaintained across the weld cable for delivery to the weld upon closureof the contactor in the wire feeder and triggering of the welding gun ortorch. In this regard, upon commencement of a welding-type process 54,70, the controller will enter a standby mode with respect to thereception of remote control commands and wait for a non-welding intervalat 72. During the non-welding interval 72, the OCV will bere-established at 52 and the controller will re-execute steps 58-68 asdescribed above following a re-verification that welding has notre-commenced at 54, 56. As such, during re-establishment of the OCV, thepower source will be periodically disabled and during these periods ofdisablement, the transceiver will, if transmitted from the wire feeder,receive remote control commands to be processed and implemented by thecontroller in regulating operation of the power source.

FIG. 4 has been described with respect to the transmission of controlcommands from the wire feeder to the power source across the weld cableduring non-welding intervals. It is also contemplated, however, thatcontrol commands may also be transmitted across the weld cable from thepower source to the wire feeder during these non-welding intervals. Inthis regard, the present invention supports bi-directional communicationbetween the power source and wire feeder. It is contemplated, however,that the advantages of the present invention may also be achieved with auni-directional system.

Referring now to FIG. 5, an exemplary circuit schematic illustratinganother embodiment of the present invention is shown. Circuit 74provides a general topology for providing an offset voltage to the OCVotherwise present between the power source and the wire feeder duringnon-welding intervals. In contrast to the periodic disabling of thepower source output to receive control data, the circuit of FIG. 5 isdesigned to provide an offset to the OCV whereby the voltage offset isused to convey control data between the remote wire feeder and the powersource. While a particular exemplary circuit will be described, it isrecognized that other circuit topologies apart from that specificallyillustrated in FIG. 5 may be used to provide a voltage offset for thetransmission of control or operational data.

As shown in FIG. 5, the remote transmission of operational and/orcontrol data in accordance with the present invention includes atransmission circuit 76 and a reception circuit 78 connected to oneanother across weld cable. The transmission circuit 76 resides in thewire feeder 14, FIG. 3, whereas the reception circuit 78, FIG. 5,resides in the power source 12. In the transmission circuit 76, atransmitter 80 is designed to provide a transient signal encoded and/ormodulated with operational control data to be transmitted to thecontroller of the power source. The transient signal has a voltagesufficient to overcome diode D2 such that the voltage at node 82 exceedsthe OCV. In this regard, a DC with transient voltage signal is input tolinear operational amplifier 84 across weld cable 16, FIG. 3,schematically represented in lead line 86, FIG. 5. The DC portion ofinput 82 is then filtered out using a capacitive element C3 such thatthe input to operational amplifier 84 is limited to the transientsignal. The operational amplified 84 then provides a single output 85that is the difference between the pair of inputs to the operationalamplifier. Specifically, the output is equal to the transient voltageinput to the linear op-amp. As such, for example, if transmitter 80provides a transient signal of seven volts coupled with a DC voltage of80 volts, then the output provided by the operational amplifier willhave a voltage of seven volts. The data embodied in this seven voltssignal may then be processed by the controller to adjust the operatingparameters of the power source consistent with those parameters input atthe wire feeder.

One skilled in the art will fully appreciate that the resistive valuesselected for R4, R5, R6, and R7 are relatively arbitrary, but arepreferably selected such that a unity gain factor is present at theoutput 85. Additionally, when the transmitter 80 is not applyingproviding a transient voltage, the OCV, which is DC, is seen across theweld cable, but filtered out by capacitive elements C2 and C3. As such,a negligible output is provided at 85. Further, during these intervalswhen the transmitter is not providing a transient voltage, the OCV isused to charge one or more capacitors or other energy storage devices(not shown) in the wire feeder, generally referenced at C_bulk. In thisregard, the OCV is used to power the electronics of the wire feeder.

While the present invention has been described with respect to abattery-less wire feeder, it is contemplated that a DC energy source maybe used to separately power the electronics of the wire feeder and thusavoid the need for a contactor in the wire feeder. In this regard, acontactor in the power source is used to control the presence of the OCVbetween the power source and the wire feeder. As such, the contactor inthe power source may be closed to create a voltage potential between thewelding torch and the power source. This OCV may be temporarilyinterrupted to receive control commands or used as a communications linkbetween the power source and wire feeder as heretofore described.

Additionally, the present invention contemplates the incorporation of astate machine or other processing device to ignore, for a pre-setperiod, changes in current at initiation of welding. That is, absentsuch a state machine, the controller may interpret initial changes incurrent at welding start-up as an arc outage. As such, the presentinvention also is directed to the incorporation of a timed loop wherebyinitial changes in current are ignored for a fixed period of time after,i.e. 100 msec., after welding start-up. Such a system is in contrast toknown systems that may be susceptible to false detection of arc outages.With these systems, the power source may try to power down to anon-welding state in response to a rapid change in current,notwithstanding that the operator has initiated a welding event.Accordingly, the controller in the power source is further configured tocontrol the power source to enter a start-up state when the gun triggeris pressed, but not allow transition to an “arc end” state until thepre-set time has expired.

Therefore, the present invention includes a welding system. The weldingsystem includes a battery-less wire feeder designed to feed consumablematerial to a weld and a power source designed to provide a weldingpower and having a power output connected to the battery-less wirefeeder via a weld cable. The welding system includes a controller toperiodically disable the power output and receive power source controlcommands from the battery-less wire feeder across the weld cable whenthe power output is disabled.

A MIG welder is disclosed and includes a wire feeder designed to deliverconsumable welding wire to a weld. A power source is connected to thewire feeder via a weld cable. The weld cable is designed to carry an OCVthereacross during standby operation of the wire feeder. The MIG welderincludes a communications link between the wire feeder and the powersource extending across the weld cable. The communications link isdesigned to translate control commands between the power source and wirefeeder manifested in a voltage offset from the OCV.

The invention also includes a method of remotely controlling a weldingprocess. The method includes the steps of periodically disabling anoutput of a power source designed to provide welding power to a weld andreceiving control commands from a wire feeder remote from the powersource when the output of the power source is disabled. The methodfurther includes the step of, following reception of the controlcommands, re-enabling the output of the power source to provide power tothe weld at a level consistent with that embodied in the controlcommands.

As stated above, the present invention is also applicable with non-MIGwelding systems such as TIG and stick welders. Further, theaforedescribed circuitry may be implemented to automatically adjust theoutput of a power source to compensate for losses that occur across weldcables. That is, in some manufacturing and/or industrial settings, theweld is a relatively great distance from the power source. As such, theweld cables may be dozens to over a hundred feet in length. This weldcable length results in losses from the output terminal of the powersource to the weld. Simply, the voltage at the output terminals of thepower source (where the weld cable is connected to the power source) maybe significantly more than the voltage across the weld. Accordingly, thepresent invention may be used to transmit a voltage feedback signal atthe weld to the power source whereupon a controller in the power sourcecompares the voltage at the terminal to the voltage at the weld andadjusts the voltage at the terminal such that after the lossesexperienced across the weld cables, the voltage at the weld is at thelevel requested by the user.

As one skilled in the art will fully appreciate, the heretoforedescription of welding devices not only includes welders, but alsoincludes any system that requires high power outputs, such as heatingand cutting systems. Therefore, the present invention is equivalentlyapplicable with any device requiring high power output, includingwelders, plasma cutters, induction heaters, aircraft ground power units,and the like. Reference to welding power, welding-type power, or weldersgenerally, includes welding, cutting, heating power, or ground power foraircraft. Description of a welding apparatus illustrates just oneembodiment in which the present invention may be implemented. Thepresent invention is equivalently applicable with many high powersystems, such as cutting and induction heating systems, aircraft groundpower systems or any similar systems.

The present invention has been described in terms of the preferredembodiment, and it is recognized that equivalents, alternatives, andmodifications, aside from those expressly stated, are possible andwithin the scope of the appending claims.

1. A welding system comprising: a wire feeder constructed to feedconsumable material to a weld; a power source having a power outputconnected to the wire feeder via a weld cable to provide a welding powerthereacross during a welding process and to provide an open circuitvoltage (OCV) across the weld cable during a standby operation of thewire feeder; a circuit constructed to provide a transient signal to theOCV, the transient signal having control data to adjust operatingparameters of the power source; and a controller connected to the powersource to process the transient signal.
 2. The welding system of claim 1wherein the transient signal is encoded or modulated with control datato be transmitted to the controller.
 3. The welding system of claim 1wherein the controller resides in the power source.
 4. The weldingsystem of claim 1 wherein the OCV is used to provide power to aplurality of electronics of the wire feeder when the transient signal issubstantially absent.
 5. The welding system of claim 1 wherein the wirefeeder is a battery-less wire feeder.
 6. The welding system of claim 5wherein the circuit is further constructed to provide the OCV and thetransient signal to the controller as a combined voltage.
 7. The weldingsystem of claim 5 wherein the circuit is incorporated into at least oneof the wire feeder and the power source.
 8. A MIG welder comprising: awire feeder to deliver a consumable welding wire to a weld; a powersource connected to the wire feeder via a weld cable, the weld cablehaving an open circuit voltage (OCV) thereacross during a standbyoperation of the wire feeder; and a communications link between the wirefeeder and the power source extending across the weld cable, thecommunications link translating control commands between the powersource and the wire feeder manifested in a voltage offset from the OCV.9. The MIG welding of claim 8 wherein the power source includes acontroller connected to the communications link to control the powersource and provide one of current output at a given constant amplitudeand voltage output at a given constant amplitude based on controlcommands received from the wire feeder across the communications link.10. The MIG welder of claim 8 wherein the wire feeder includes aplurality of electronics designed to control operation of the wirefeeder and wherein the plurality of electronics is powered by the OCVduring the standby operation of the wire feeder.
 11. The MIG welder ofclaim 8 wherein the communications link is configured to encode thecontrol commands with at least one of voltage encoding and frequencyencoding.
 12. The MIG welder of claim 8 wherein the communications linkis configured to serialize communication between the wire feeder andpower source.
 13. The MIG welder of claim 8 wherein the wire feeder isconnected to a welding gun having a trigger, and wherein the wire feederincludes a contactor assembly designed to close to a conductive statewhen the trigger is selected to deliver welding power to the weldinggun.
 14. A method of controlling a welding process, the methodcomprising the steps of: providing a DC signal across a weld cableduring non-welding intervals, the weld cable connecting a power sourcewith a wire feeder; encoding control commands onto the DC signal acrossthe weld cable; and processing the control commands to adjust operatingparameters of the power source.
 15. The method of claim 14 furthercomprising the step of receiving the control commands from a user inputconnected to the wire feeder.
 16. The method of claim 14 wherein thecontrol commands are encoded or modulated in a transient signal.
 17. Themethod of claim 16 further comprising the step of substantiallyfiltering out the DC signal from the transient signal.
 18. The method ofclaim 16 wherein the transient signal has a voltage sufficient to exceedthe DC signal.
 19. The method of claim 14 further comprising the step ofusing the DC signal to provide power to a plurality of electronics ofthe wire feeder.
 20. The method of claim 14 wherein the DC signal is anopen circuit voltage.
 21. A MIG welder comprising: a wire feederdesigned to deliver consumable welding wire to a weld; a power sourcehaving a power source output; a weld cable connecting the wire feederand the power source, the weld cable designed to carry a welding powerfrom the power source to the wire feeder and further designed to carryat least one-way control commands transmitted therebetween the powersource and the wire feeder; and wherein the at least one-way controlcommands are carried when the power source output is interrupted. 22.The MIG welder of claim 21 wherein the power source output interruptionis triggered by an OCV between the power source and the wire feeder. 23.The MIG welder of claim 21 further comprising a plurality of electronicsthat re-establish the power source output after the power source outputinterruption.
 24. The MIG welder of claim 21 wherein the power sourceoutput interruption does not occur when a welding process is beingactively carried out.
 25. The MIG welder of claim 21 wherein at leastone-way control commands are transmitted from at least one of the powersource and the wire feeder.
 26. The MIG welder of claim 25 wherein thepower source output is interrupted at an initiation of a welding processto allow for the transmission of the at least one-way control commands.